Siemens Aktiengesellschaft

Gpt Limited

Robert K Galpin

Robert Lechner

Hans-Werner Rudolf

Nigel P Dyer

Pierre Albouy

Harald Stader

Norbert Wingerath

Virgilio Mosca

Antonio Nicastro

Ramatchandirane Nadaradjane

Christopher C Priest

Robert Le Gougnec

Marcello Manca

There is a demand for user access to ISDN services at the two-wire interface point. The frequently raised objection to such access is the problem of determining the location of a fault and hence the responsibility for the fault. This is solved by the use of a voltage sensor responsive to a DC voltage less than a normal line feed voltage within a voltage range not used in normal operation to control a switch operative to disconnect a subscriber termination unit from the line, and to provide a known linear terminating impedance for the line for the duration of the application of the DC voltage.

Termination unit with maintenance facility

Circuitry is provided for testing telephone lines, the circuitry comprising a loop current ring trip detector and a relay which in operation is used to break normal current to provide an end of call indication, and wherein said relay is also operative in one test mode to switch from said loop current ring detector to a comparator which functions as a test mode detector. The means may also include a second relay which when the circuit is in a second test mode is operated simultaneously with the first relay, the second relay being connected to a bell capacitor the discharge rate of which can be measured by said capacitor, and the comparator output is sequentially monitored to provide information as to the condition of the insulation and regarding bell capacitor and terminal connection.

Remote line test facility

A digital interface between at least two subscriber line interface circuits and a processing unit is described. The interface is configured in the form of a parallel interface. The level of an input/output register and of a control register is allocated, as needed, to the connections of the processing unit. These connections can be operated selectively as inputs or outputs. They can also be operated in two modes, depending upon which type of subscriber line interface circuit (SLIC) is connected. The connections of the last-mentioned units are partially operable as inputs or outputs and partially operable only as inputs but in the input case, selectively for various types of input signals.

Digital interface between at least two subscriber line interface

A digital interface of an integrated subscriber line interface circuit is provided. The interface serves for the connection of a signal processor unit. Individual connections are used as signal inputs in signal entry operation of the interface, and as signal outputs in signal transmission operation. Other connections are used as signal inputs in both operating mode, but receive different signals in each operating mode. One group of connections includes two registers with respective associated decoders to enable switching from one to the other, so that the number of operating instructions that can be represented by means of binary signal value combinations applied to the connections is doubled.

Digital interface of an integrated subscriber line interface circuit

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Knutsford, United Kingdom

Robert K Galpin